#include<bits/stdc++.h>
using namespace std;
using Int=long long;
using Real=long double;
template<class T,class S>inline bool chmin(T&A,S B){if(A>B){A=B;return true;}else{return false;}}
template<class T,class S>inline bool chmax(T&A,S B){if(A<B){A=B;return true;}else{return false;}}
#define REP(i,n)for(int i=0;i<(n);++i)
#define REP1(i,n)for(int i=1;i<=(n);++i)
#define ALL(x)begin(x),end(x)
#define drop(x){cout<<(x)<<'\n';return;}
int N;
string S[101][101];
void sol()
{
	cin>>N;
	REP(i,N)REP(j,N)cin>>S[i][j];
	int ans=-1,cnt=0;
	REP(i,N)
	{
		bool ok=true;
		REP(j,N)
		{
			ok&=i==j||S[j][i]=="nyanpass";
		}
		if(ok)ans=i+1,++cnt;
	}
	if(cnt>=2)ans=-1;
	cout<<ans<<"\n";
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cout.tie(nullptr);
	cout<<fixed<<setprecision(1);
	int TE=1;
	//cin>>TE;
	while(TE--)sol();
}